Difference between revisions of "Programming/OpenMPI"
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* ORTE - the Open Run-Time Environment | * ORTE - the Open Run-Time Environment | ||
* OPAL - the Open Portable Access Layer | * OPAL - the Open Portable Access Layer | ||
| + | |||
| + | === Program Example === | ||
| + | |||
| + | <pre style="background-color: #C8C8C8; color: black; border: 2px solid black; font-family: monospace, sans-serif;"> | ||
| + | |||
| + | #include <mpi.h> | ||
| + | #include <stdio.h> | ||
| + | |||
| + | int main(int argc, char** argv) | ||
| + | { | ||
| + | int rank; | ||
| + | int buf; | ||
| + | MPI_Status status; | ||
| + | MPI_Init(&argc, &argv); | ||
| + | MPI_Comm_rank(MPI_COMM_WORLD, &rank); | ||
| + | |||
| + | if(rank == 0) | ||
| + | { | ||
| + | buf = 777; | ||
| + | MPI_Bcast(&buf, 1, MPI_INT, 0, MPI_COMM_WORLD); | ||
| + | } | ||
| + | else | ||
| + | { | ||
| + | MPI_Recv(&buf, 1, MPI_INT, 0, 0, MPI_COMM_WORLD, &status); | ||
| + | printf("rank %d receiving received %d\n", rank, buf); | ||
| + | } | ||
| + | MPI_Finalize(); | ||
| + | return 0; | ||
| + | } | ||
| + | |||
| + | </pre> | ||
| + | |||
| + | === Compilation === | ||
| + | |||
| + | <pre style="background-color: #C8C8C8; color: black; border: 2px solid black; font-family: monospace, sans-serif;"> | ||
| + | |||
| + | gcc -o test2 -fopenmp test2.c | ||
| + | |||
| + | </pre> | ||
| + | |||
== Usage Examples == | == Usage Examples == | ||
Revision as of 15:11, 30 January 2017
Contents
Programming Details
MPI defines not only point-to-point communication (e.g., send and receive), it also defines other communication patterns, such as collective communication. Collective operations are where multiple processes are involved in a single communication action. Reliable broadcast, for example, is where one process has a message at the beginning of the operation, and at the end of the operation, all processes in a group have the message.
Message-passing performance and resource utilization are the king and queen of high-performance computing. Open MPI was specifically designed in such a way that it could operate at the very bleeding edge of high performance: incredibly low latencies for sending short messages, extremely high short message injection rates on supported networks, fast ramp-ups to maximum bandwidth for large messages, etc.
The Open MPI code has 3 major code modules:
- OMPI - MPI code
- ORTE - the Open Run-Time Environment
- OPAL - the Open Portable Access Layer
Program Example
#include <mpi.h>
#include <stdio.h>
int main(int argc, char** argv)
{
int rank;
int buf;
MPI_Status status;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
if(rank == 0)
{
buf = 777;
MPI_Bcast(&buf, 1, MPI_INT, 0, MPI_COMM_WORLD);
}
else
{
MPI_Recv(&buf, 1, MPI_INT, 0, 0, MPI_COMM_WORLD, &status);
printf("rank %d receiving received %d\n", rank, buf);
}
MPI_Finalize();
return 0;
}
Compilation
gcc -o test2 -fopenmp test2.c
Usage Examples
Batch Submission
#!/bin/bash #SBATCH -J MPI-testXX #SBATCH -N 10 #SBATCH --ntasks-per-node 28 #SBATCH -D /home/user/CODE_SAMPLES/OPENMPI #SBATCH -o %N.%j.%a.out #SBATCH -e %N.%j.%a.err #SBATCH -p compute #SBATCH --exclusive echo $SLURM_JOB_NODELIST module purge module load gcc/4.9.3 module load openmpi/gcc/1.10.2 export I_MPI_DEBUG=5 export I_MPI_FABRICS=shm:tmi export I_MPI_FALLBACK=no mpirun -mca pml cm -mca mtl psm2 /home/user/CODE_SAMPLES/OPENMPI/scatteravg 100
[username@login01 ~]$ sbatch MPI-demo.job Submitted batch job 289523